Carbon dioxide is a well-known gas, which is present in the atmosphere. It is released to the atmosphere in large amounts by fermentation processes, limestone calcinations, and all forms of combustion processes of carbon and carbon compounds. In recent decades, the attention in respect of said emission has been rising, because of the environmental problem due to future climate change via the Greenhouse effect. Consequently, extensive work has been performed over the years in order to develop processes for the removal of carbon dioxide from combustion gases. If possible, a subsequent recovery of carbon dioxide may make those processes economically feasible.
One type of conventional process for the recovery of carbon dioxide from a gaseous source is the absorption process, in which carbon dioxide is absorbed in an absorbing agent. In a conventional plant, the carbon dioxide is firstly separated from the rest of the feed gas by absorbing the carbon dioxide in an absorbing agent. Afterwards, the carbon dioxide is separated from the absorbing agent. In cases where a physical absorbing agent is employed, said separation is typically performed by decreasing the pressure in a flash or stripping column. If necessary, the spent absorbing agent is then regenerated before the pressure is increased prior to recycling to the absorbing column. The treated feed gas leaving the absorption column is disposed of to the atmosphere. However, these periodical pressure rises and pressure drops increase the production costs and the investment expenditure for equipment for increasing pressure is of major considerations.
Very surprisingly the present inventors have found that it is possible to remove carbon dioxide from a feed gas, if the feed gas is fed to the stripper column instead of the absorption column. This is due to the fact that when the feed gas in the stripper column strips an absorption agent, in which carbon dioxide is absorbed, the concentration of carbon dioxide in the gas leaving the stripper column is increased. As a consequence of this increased concentration it is possible to condensate the gaseous carbon dioxide subsequently.
Another major advantage of the present invention is that it is possible to operate the plant at constant pressure. By this mode of operation the investment expenditure for providing equipment for increasing pressure is dispensed with, and no production costs for altering the pressure within the plant can be found.